Insight into aerobic phosphorus removal from wastewater in algal-bacterial aerobic granular sludge system

This study aimed to figure out the main contributors to aerobic phosphorus (P) removal in the algal-bacterial aerobic granular sludge (AGS)-based wastewater treatment system. Kinetics study showed that aerobic P removal was controlled by macropore (contributing to 64-75% P removal) and micropore diffusion, and the different light intensity (0, 4.0, 12.3, and 24.4 klux) didn't exert significant (p > 0.05) influence on P removal. On the other hand, the increasing light intensity did promote microalgae metabolism, leading to the elevated wastewater pH (8.0-9.8). The resultant pH increase had a strongly negative relationship (R2 = 0.9723) with P uptake by polyphosphate-accumulating organisms, while promoted chemical Ca-P precipitation at a molar Ca/P ratio of 1.05. Results from this work could provide an in-depth understanding of microalgae-bacteria symbiotic interaction, which is helpful to better design and operate the algal-bacterial AGS systems.